In a typical vapor compression refrigeration circuit, various components, including a compressor, two heat exchangers, and an expansion device, are arranged and operated to transfer heat from one location to another. With a heat pump configuration, refrigerant flow through the refrigeration circuit can be reversed from the refrigerant flow when the refrigeration circuit is operating in a cooling configuration so that the refrigeration circuit may transfer heat not only from a first location to a second, but also from the second location to the first. For example, a first heat exchanger may be located within a conditioned space and a second heat exchanger may be located outside the conditioned space. In a cooling configuration, heat is transferred from the first heat exchanger to the second, cooling; the conditioned space. In a heat pump configuration, heat is transferred from the second heat exchanger to the first, heating the conditioned space.